@spec get_budget(Ecto.UUID.t(), Ecto.UUID.t()) :: Ecto.Schema.t() | nil

Gets a budget by adapter and sequence version.

@spec get_or_create_budget(Ecto.UUID.t(), Ecto.UUID.t()) ::
  {:ok, Ecto.Schema.t()} | {:error, Ecto.Changeset.t() | :budget_unavailable}

Gets an existing budget or creates the default lazy budget.

Race-safe: concurrent callers go through an upsert with on_conflict: :nothing on the (adapter_id, sequence_version_id) unique index, then re-fetch.

@spec list_budgets(map()) :: [Ecto.Schema.t()]

Lists budgets for optional adapter and sequence-version filters.

@spec set_adapter_sequence_budget(Ecto.UUID.t(), Ecto.UUID.t(), map()) ::
  {:ok, Ecto.Schema.t()} | {:error, Ecto.Changeset.t()}

Creates or updates a per-adapter, per-sequence budget.

The budget's tenant_key is inherited from the adapter so tenant scope is enforced at the row level even though the unique key is (adapter_id, sequence_version_id).